This invention relates to a process for producing resin impregnated fiber reinforced materials, and is particularly concerned with novel procedure for impregnating dry fiber reinforcement, e.g. in the form of layers thereof, with a predetermined amount of resin, followed by final curing, to produce a resin impregnated reinforcement material which is essentially completely and uniformly saturated with a predetermined amount of resin.
The concept of impregnating dry fibrous materials such as glass fiber, with a resin under vacuum conditions, and curing the resin to produce a composite is known in the art, as disclosed, for example, in U.S. Pat. Nos. 3,028,284; 3,322,566; 3,384,505; 3,523,152; 3,790,432 and 4,030,953.
Most structural type composite parts are presently made from "B" stage resin impregnated woven cloth or unidirectional tape fibers such as graphite, boron, Kevlar (aramide) or glass fiber materials. The resin is partially cured or "staged" to the desired consistency for tack and handling characteristics that will allow a later heat and pressure cycle to complete the fabrication process.
However, the "B" stage fiber reinforcement materials so produced are perishable when stored and must be stored at low temperatures to preserve a useful shelf life. Further, such stored materials require frequent inspection and recertification to assure good storage quality.
It is an object of the present invention to provide a novel economical process for impregnating fiber reinforcement material with a resin so as to produce uniform impregnation of resin into the fiber reinforcement material. A further object is to provide a process of the above type wherein the fiber reinforcement material is saturated or impregnated with a predetermined desired resin content for optimum mechanical properties. A still further object is to provide a process for impregnating fiber reinforcement material and curing the resin, directly on a tool or mold, and thus by-passing the more expensive prior art operation of first forming a "pre-preg" or fiber reinforcement impregnated with "B" stage resin, which is stored prior to final curing.